Mapping two-stage sidelink control with multi-layer sidelink data channel

ABSTRACT

Certain aspects of the present disclosure provide techniques for mapping two-stage sidelink control with multiple layer sidelink data channel. A first user equipment (UE) can rate-match a multiple-layer second stage of a two-stage sidelink control information (SCI) transmission as a single layer. The first UE transmits the multiple-layer second stage of the two-stage SCI, to a second UE, using multiple antenna ports.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims benefit of and priority to U.S. ProvisionalApplication No. 62/930,930, filed Nov. 5, 2019, and to U.S. ProvisionalApplication No. 62/,915,453, filed Oct. 15, 2019, which are herebyassigned to the assignee hereof and hereby expressly incorporated byreference herein in their entireties as if fully set forth below and forall applicable purposes.

BACKGROUND Field of the Disclosure

Aspects of the present disclosure relate to wireless communications, andmore particularly, to techniques for mapping a two-stage sidelinkcontrol with a multiple layer sidelink data channel.

Description of Related Art

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,broadcasts, etc. These wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources (e.g., bandwidth,transmit power, etc.). Examples of such multiple-access systems include3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE)systems, LTE Advanced (LTE-A) systems, code division multiple access(CDMA) systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, orthogonal frequency divisionmultiple access (OFDMA) systems, single-carrier frequency divisionmultiple access (SC-FDMA) systems, and time division synchronous codedivision multiple access (TD-SCDMA) systems, to name a few.

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. New radio (e.g., 5G NR) is an exampleof an emerging telecommunication standard. NR is a set of enhancementsto the long term evolution (LTE) mobile standard promulgated by 3GPP. NRis designed to better support mobile broadband Internet access byimproving spectral efficiency, lowering costs, improving services,making use of new spectrum, and better integrating with other openstandards using OFDMA with a cyclic prefix (CP) on the downlink (DL) andon the uplink (UL). To these ends, NR supports beamforming,multiple-input multiple-output (MIMO) antenna technology, and carrieraggregation.

However, as the demand for mobile broadband access continues toincrease, there exists a need for further improvements in NR and LTEtechnology. Preferably, these improvements should be applicable to othermulti-access technologies and the telecommunication standards thatemploy these technologies.

SUMMARY

The systems, methods, and devices of the disclosure each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this disclosure as expressedby the claims that follow, some features will now be discussed briefly.After considering this discussion, and particularly after reading thesection entitled “Detailed Description” one will understand how thefeatures of this disclosure provide advantages that include improvedsidelink control information (SCI) transmission.

One or more aspects of the subject matter described in this disclosurecan be implemented in a method for wireless communication by a firstuser equipment (UE). The method generally includes rate-matching amultiple-layer second stage of a two-stage SCI transmission as a singlelayer. The method generally includes transmitting the multiple-layersecond stage of the two-stage SCI, to a second UE, using multipleantenna ports.

One or more aspects of the subject matter described in this disclosurecan be implemented in an apparatus for wireless communication. Theapparatus generally includes at least one processor and a memory coupledto the at least one processor. The memory generally includes codeexecutable by the at least one processor to cause the apparatus torate-match a multiple-layer second stage of a two-stage SCI transmissionas a single layer. The memory generally includes code executable by theat least one processor to cause the apparatus to transmit themultiple-layer second stage of the two-stage SCI, to a UE, usingmultiple antenna ports.

One or more aspects of the subject matter described in this disclosurecan be implemented in an apparatus for wireless communication. Theapparatus generally includes means for rate-matching a multiple-layersecond stage of a two-stage SCI transmission as a single layer. Theapparatus generally includes means for transmitting the multiple-layersecond stage of the two-stage SCI, to a UE, using multiple antennaports.

One or more aspects of the subject matter described in this disclosurecan be implemented in a computer readable medium storing computerexecutable code thereon for wireless communication. The computerreadable medium generally stores code for rate-matching a multiple-layersecond stage of a two-stage SCI transmission as a single layer. Thecomputer readable medium generally stores code for transmitting themultiple-layer second stage of the two-stage SCI, to a UE, usingmultiple antenna ports.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe appended drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description,briefly summarized above, may be had by reference to aspects, some ofwhich are illustrated in the drawings. It is to be noted, however, thatthe appended drawings illustrate only certain typical aspects of thisdisclosure and are therefore not to be considered limiting of its scope,for the description may admit to other equally effective aspects.

FIG. 1 is a block diagram conceptually illustrating an exampletelecommunications system, in accordance with certain aspects of thepresent disclosure.

FIG. 2 is a block diagram conceptually illustrating a design of anexample a base station (BS) and user equipment (UE), in accordance withcertain aspects of the present disclosure.

FIG. 3 is an example frame format for new radio (NR), in accordance withcertain aspects of the present disclosure.

FIG. 4 illustrates an example vehicle-to-everything (V2X) communicationsystem, in accordance with certain aspects of the present disclosure.

FIG. 5 illustrates an example V2X communication system, in accordancewith certain aspects of the present disclosure.

FIG. 6 is a diagram illustrating example sidelink data demodulationreference signal (DMRS) and two-stage sidelink control information (SCI)transmission in a slot, in accordance with certain aspects of thepresent disclosure.

FIG. 7 is a flow diagram illustrating example operations by a UE formapping a two-stage SCI transmission with a multiple-layer sidelink datachannel, in accordance with certain aspects of the present disclosure.

FIG. 8 illustrates an example communications device that may includevarious components configured to perform operations for the techniquesdisclosed herein in accordance with aspects of the present disclosure.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in one aspectmay be beneficially utilized on other aspects without specificrecitation.

DETAILED DESCRIPTION

Aspects of the present disclosure provide apparatus, methods, processingsystems, and computer readable mediums for mapping two-stage sidelinkcontrol with a multiple-layer sidelink data channel. As will bedescribed, the techniques presented herein allow mapping of the secondstage of a two-stage sidelink control information (SCI) that isdemodulated using demodulation reference signals (DMRS) of amultiple-layer sidelink data channel, even when the SCI and PSSCH have adifferent number of layers.

The following description provides examples of mapping two-stagesidelink control with multi-layer sidelink data channel that may be usedfor sidelink in communication systems, and is not limiting of the scope,applicability, or examples set forth in the claims. Changes may be madein the function and arrangement of elements discussed without departingfrom the scope of the disclosure. Various examples may omit, substitute,or add various procedures or components as appropriate. For instance,the methods described may be performed in an order different from thatdescribed, and various steps may be added, omitted, or combined. Also,features described with respect to some examples may be combined in someother examples. For example, an apparatus may be implemented or a methodmay be practiced using any number of the aspects set forth herein. Inaddition, the scope of the disclosure is intended to cover such anapparatus or method that is practiced using other structure,functionality, or structure and functionality in addition to, or otherthan, the various aspects of the disclosure set forth herein. It shouldbe understood that any aspect of the disclosure disclosed herein may beembodied by one or more elements of a claim. The word “exemplary” isused herein to mean “serving as an example, instance, or illustration.”Any aspect described herein as “exemplary” is not necessarily to beconstrued as preferred or advantageous over other aspects.

In general, any number of wireless networks may be deployed in a givengeographic area. Each wireless network may support a particular radioaccess technology (RAT) and may operate on one or more frequencies. ARAT may also be referred to as a radio technology, an air interface,etc. A frequency may also be referred to as a carrier, a subcarrier, afrequency channel, a tone, a subband, etc. Each frequency may support asingle RAT in a given geographic area in order to avoid interferencebetween wireless networks of different RATs.

The techniques described herein may be used for various wirelessnetworks and radio technologies me. For clarity, while aspects may bedescribed herein using terminology commonly associated with 3G, 4G,and/or new radio (e.g., 5G NR) wireless technologies, aspects of thepresent disclosure can be applied in other generation-basedcommunication systems.

NR access may support various wireless communication services, such asenhanced mobile broadband (eMBB) targeting wide bandwidth (e.g., 80 MHzor beyond), millimeter wave (mmW) targeting high carrier frequency(e.g., 25 GHz or beyond), massive machine type communications MTC (mMTC)targeting non-backward compatible MTC techniques, and/or missioncritical targeting ultra-reliable low-latency communications (URLLC).These services may include latency and reliability requirements. Theseservices may also have different transmission time intervals (TTI) tomeet respective quality of service (QoS) requirements. In addition,these services may co-exist in the same subframe.

NR may also support beamforming and beam direction may be dynamicallyconfigured. Multiple-input multiple-output (MIMO) transmissions withprecoding may also be supported. In some examples, MIMO configurationsin the DL may support up to 8 transmit antennas with multi-layer DLtransmissions up to 8 streams and up to 2 streams per UE. In someexamples, multi-layer transmissions with up to 2 streams per UE may besupported. Aggregation of multiple cells may be supported with up to 8serving cells.

FIG. 1 illustrates an example wireless communication network 100 inwhich aspects of the present disclosure may be performed. For example,the wireless communication network 100 may be an NR system (e.g., a 5GNR network). As shown in FIG. 1, the wireless communication network 100may be in communication with a core network 132. The core network 132may in communication with one or more base station (BSs) 110 and/or userequipment (UE) 120 in the wireless communication network 100 via one ormore interfaces.

A BS 110 may provide communication coverage for a particular geographicarea, sometimes referred to as a “cell”, which may be stationary or maymove according to the location of a mobile BS 110. In some examples, theBSs 110 may be interconnected to one another and/or to one or more otherBSs or network nodes (not shown) in wireless communication network 100through various types of backhaul interfaces (e.g., a direct physicalconnection, a wireless connection, a virtual network, or the like) usingany suitable transport network. In the example shown in FIG. 1, the BSs110 a, 110 b and 110 c may be macro BSs for the macro cells 102 a, 102 band 102 c, respectively. The BS 110 x may be a pico BS for a pico cell102 x. The BSs 110 y and 110 z may be femto BSs for the femto cells 102y and 102 z, respectively. A BS may support one or multiple cells. TheBSs 110 communicate with user equipment (UEs) 120 a-y (each alsoindividually referred to herein as UE 120 or collectively as UEs 120) inthe wireless communication network 100. The UEs 120 (e.g., 120 x, 120 y,etc.) may be dispersed throughout the wireless communication network100, and each UE 120 may be stationary or mobile.

According to certain aspects, the UEs 120 may be configured for sidelinkcommunications. As shown in FIG. 1, the UE 110 a includes a SCI manager122 a and the UE 120 b includes a SCI manager 122 b. The SCI manager 122a and/or the SCI manager 122 b may be configured to map, transmit,receive, demap, and/or demodulate a two-stage SCI with a multi-layersidelink data channel, in accordance with aspects of the presentdisclosure. As discussed in more detail below, the SCI manager 122 aand/or the SCI manager 122 b may rate-match the second stage oftwo-stage SCI to as a single layer and map the second stage of thetwo-stage SCI to multiple antenna ports.

Wireless communication network 100 may also include relay stations(e.g., relay station 110 r), also referred to as relays or the like,that receive a transmission of data and/or other information from anupstream station (e.g., a BS 110 a or a UE 120 r) and sends atransmission of the data and/or other information to a downstreamstation (e.g., a UE 120 or a BS 110), or that relays transmissionsbetween UEs 120, to facilitate communication between devices.

A network controller 130 may couple to a set of BSs 110 and providecoordination and control for these BSs 110. The network controller 130may communicate with the BSs 110 via a backhaul. The BSs 110 may alsocommunicate with one another (e.g., directly or indirectly) via wirelessor wireline backhaul.

FIG. 2 illustrates example components of BS 110 a and UE 120 a (e.g., inthe wireless communication network 100 of FIG. 1, which may be similarcomponents in the UE 120 b), which may be used to implement aspects ofthe present disclosure.

At the BS 110 a, a transmit processor 220 may receive data from a datasource 212 and control information from a controller/processor 240. Thecontrol information may be for the physical broadcast channel (PBCH),physical control format indicator channel (PCFICH), physical hybrid ARQindicator channel (PHICH), physical downlink control channel (PDCCH),group common PDCCH (GC PDCCH), etc. The data may be for the physicaldownlink shared channel (PDSCH), etc. A medium access control(MAC)-control element (MAC-CE) is a MAC layer communication structurethat may be used for control command exchange between wireless nodes.For example, a BS may transmit a MAC CE to a UE to put the UE into adiscontinuous reception (DRX) mode to reduce the UE's power consumption.The MAC-CE may be carried in a shared channel such as a physicaldownlink shared channel (PDSCH), a physical uplink shared channel(PUSCH), or a physical sidelink shared channel. A MAC-CE may also beused to communicate information that facilitates communication, such asinformation regarding buffer status and available power headroom.

The processor 220 may process (e.g., encode and symbol map) the data andcontrol information to obtain data symbols and control symbols,respectively. The transmit processor 220 may also generate referencesymbols, such as for the primary synchronization signal (PSS), secondarysynchronization signal (SSS), and channel state information referencesignal (CSI-RS). A transmit (TX) multiple-input multiple-output (MIMO)processor 230 may perform spatial processing (e.g., precoding) on thedata symbols, the control symbols, and/or the reference symbols, ifapplicable, and may provide output symbol streams to the modulators(MODs) 232 a-232 t. Each modulator 232 may process a respective outputsymbol stream (e.g., for OFDM, etc.) to obtain an output sample stream.Each modulator may further process (e.g., convert to analog, amplify,filter, and upconvert) the output sample stream to obtain a downlinksignal. Downlink signals from modulators 232 a-232 t may be transmittedvia the antennas 234 a-234 t, respectively.

At the UE 120 a, the antennas 252 a-252 r may receive the downlinksignals from the BS 110 a, or sidelink signals from the UE 120 b, andmay provide received signals to the demodulators (DEMODs) intransceivers 254 a-254 r, respectively. Each demodulator may condition(e.g., filter, amplify, downconvert, and digitize) a respective receivedsignal to obtain input samples. Each demodulator may further process theinput samples (e.g., for OFDM, etc.) to obtain received symbols. A MIMOdetector 256 may obtain received symbols from all the demodulators intransceivers 254 a-254 r, perform MIMO detection on the received symbolsif applicable, and provide detected symbols. A receive processor 258 mayprocess (e.g., demodulate, deinterleave, and decode) the detectedsymbols, provide decoded data for the UE 120 a to a data sink 260, andprovide decoded control information to a controller/processor 280.

On the uplink or sidelink, at UE 120 a, a transmit processor 264 mayreceive and process data (e.g., for the physical uplink shared channel(PUSCH)) from a data source 262 and control information (e.g., for thephysical uplink control channel (PUCCH) from the controller/processor280. The transmit processor 264 may also generate reference symbols fora reference signal (e.g., for the sounding reference signal (SRS)). Thesymbols from the transmit processor 264 may be precoded by a TX MIMOprocessor 266 if applicable, further processed by the modulators intransceivers 254 a-254 r (e.g., for SC-FDM, etc.), and transmitted tothe BS 110 a. At the BS 110 a, the uplink signals from the UE 120 a maybe received by the antennas 234, processed by the demodulators intransceivers 232 a-232 t, detected by a MIMO detector 236 if applicable,and further processed by a receive processor 238 to obtain decoded dataand control information sent by the UE 120 a. The receive processor 238may provide the decoded data to a data sink 239 and the decoded controlinformation to the controller/processor 240.

The memories 242 and 282 may store data and program codes for BS 110 aand UE 120 a, respectively. A scheduler 244 may schedule UEs for datatransmission on the downlink and/or uplink.

Antennas 252, processors 266, 258, 264, and/or controller/processor 280of the UE 120 a and/or antennas 234, processors 220, 230, 238 may beused to perform the various techniques and methods described herein. Thecontroller/processor 280 and/or other processors and modules at the UE120 a may perform or direct the execution of processes for thetechniques described herein. For example, as shown in FIG. 2, thecontroller/processor 280 of the UE 120 a has a SCI manager 222 that maybe configured map, transmit, receive, demap, and/or demodulate atwo-stage SCI with a multi-layer sidelink data channel, in accordancewith aspects of the present disclosure. As discussed in more detailbelow, the SCI manager 222 may rate-match the second stage of two-stageSCI to as a single layer and map the second stage of the two-stage SCIto multiple antenna ports. Although shown at the controller/processor,other components of the UE 120 a may be used to perform the operationsdescribed herein.

NR may utilize orthogonal frequency division multiplexing (OFDM) with acyclic prefix (CP) on the uplink and downlink. NR may supporthalf-duplex operation using time division duplexing (TDD). OFDM andsingle-carrier frequency division multiplexing (SC-FDM) partition thesystem bandwidth into multiple orthogonal subcarriers, which are alsocommonly referred to as tones, bins, etc. Each subcarrier may bemodulated with data. Modulation symbols may be sent in the frequencydomain with OFDM and in the time domain with SC-FDM. The spacing betweenadjacent subcarriers may be fixed, and the total number of subcarriersmay be dependent on the system bandwidth. The minimum resourceallocation, called a resource block (RB), may be 12 consecutivesubcarriers. The system bandwidth may also be partitioned into subbands.For example, a subband may cover multiple RBs. NR may support a basesubcarrier spacing (SCS) of 15 KHz and other SCS may be defined withrespect to the base SCS (e.g., 30 kHz, 60 kHz, 120 kHz, 240 kHz, etc.).

FIG. 3 is a diagram showing an example of a frame format 300 for NR. Thetransmission timeline for each of the downlink and uplink may bepartitioned into units of radio frames. Each radio frame may have apredetermined duration (e.g., 10 ms) and may be partitioned into 10subframes, each of 1 ms, with indices of 0 through 9. Each subframe mayinclude a variable number of slots (e.g., 1, 2, 4, 8, 16, . . . slots)depending on the SCS. Each slot may include a variable number of symbolperiods (e.g., 7 or 14 symbols) depending on the SCS. The symbol periodsin each slot may be assigned indices. A mini-slot, which may be referredto as a sub-slot structure, refers to a transmit time interval having aduration less than a slot (e.g., 2, 3, or 4 symbols). Each symbol in aslot may indicate a link direction (e.g., DL, UL, or flexible) for datatransmission and the link direction for each subframe may be dynamicallyswitched. The link directions may be based on the slot format. Each slotmay include DL/UL data as well as DL/UL control information.

In NR, a synchronization signal block (SSB) is transmitted. In certainaspects, SSBs may be transmitted in a burst where each SSB in the burstcorresponds to a different beam direction for UE-side beam management(e.g., including beam selection and/or beam refinement). The SSBincludes a PSS, a SSS, and a two symbol PBCH. The SSB can be transmittedin a fixed slot location, such as the symbols 0-3 has shown in FIG. 3.The PSS and SSS may be used by UEs for cell search and acquisition. ThePSS may provide half-frame timing, the SS may provide the CP length andframe timing. The PSS and SSS may provide the cell identity. The PBCHcarries some basic system information, such as downlink systembandwidth, timing information within radio frame, SS burst setperiodicity, system frame number, etc. The SSBs may be organized into SSbursts to support beam sweeping. Further system information such as,remaining minimum system information (RMSI), system information blocks(SIBs), other system information (OSI) can be transmitted on a physicaldownlink shared channel (PDSCH) in certain subframes. The SSB can betransmitted up to sixty-four times, for example, with up to sixty-fourdifferent beam directions for mmWave. The multiple transmissions of theSSB are referred to as a SS burst set. SSBs in an SS burst set may betransmitted in the same frequency region, while SSBs in different SSbursts sets can be transmitted at different frequency regions.

In some examples, access to the air interface may be scheduled. Ascheduling entity (e.g., a BS 110) allocates resources for communicationamong some or all devices and equipment within its service area or cell.The scheduling entity may be responsible for scheduling, assigning,reconfiguring, and releasing resources for one or more subordinateentities. That is, for scheduled communication, subordinate entitiesutilize resources allocated by the scheduling entity. BSs 110 are notthe only entities that may function as a scheduling entity. In someexamples, a UE 120 may function as a scheduling entity and may scheduleresources for one or more subordinate entities (e.g., one or more otherUEs 120), and the other UEs 120 may utilize the resources scheduled bythe UE 120 for wireless communication. In some examples, a UE 120 mayfunction as a scheduling entity in a peer-to-peer (P2P) network, and/orin a mesh network. In a mesh network example, UEs 120 may communicatedirectly with one another in addition to communicating with a schedulingentity.

In some examples, the communication between the UEs 120 and BSs 110 isreferred to as the access link. The access link may be provided via a Uuinterface. Communication between devices may be referred as thesidelink.

In some examples, two or more subordinate entities (e.g., UEs 120) maycommunicate with each other using sidelink signals. Real-worldapplications of such sidelink communications may include public safety,proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V)communications, Internet of Everything (IoE) communications, IoTcommunications, mission-critical mesh, and/or various other suitableapplications. Generally, a sidelink signal may refer to a signalcommunicated from one subordinate entity (e.g., UE 120 a) to anothersubordinate entity (e.g., another UE 120) without relaying thatcommunication through the scheduling entity (e.g., UE 120 or BS 110),even though the scheduling entity may be utilized for scheduling and/orcontrol purposes. In some examples, the sidelink signals may becommunicated using a licensed spectrum (unlike wireless local areanetworks, which typically use an unlicensed spectrum). One example ofsidelink communication is PC5, for example, as used in V2V, LTE, and/orNR.

Various sidelink channels may be used for sidelink communications,including a physical sidelink discovery channel (PSDCH), a physicalsidelink control channel (PSCCH), a physical sidelink shared channel(PSSCH), and a physical sidelink feedback channel (PSFCH). The PSDCH maycarry discovery expressions that enable proximal devices to discovereach other. The PSCCH may carry control signaling such as sidelinkresource configurations and other parameters used for datatransmissions, and the PSSCH may carry the data transmissions. The PSFCHmay carry feedback such as CSI related to a sidelink channel quality.

FIG. 4 and FIG. 5 show diagrammatic representations of example V2Xsystems, in accordance with some aspects of the present disclosure. Forexample, the vehicles shown in FIG. 4 and FIG. 5 may communicate viasidelink channels and may perform sidelink CSI reporting as describedherein.

The V2X systems, provided in FIG. 4 and FIG. 5 provide two complementarytransmission modes. A first transmission mode, shown by way of examplein FIG. 4, involves direct communications (for example, also referred toas side link communications) between participants in proximity to oneanother in a local area. A second transmission mode, shown by way ofexample in FIG. 5, involves network communications through a network,which may be implemented over a Uu interface (for example, a wirelesscommunication interface between a radio access network (RAN) and a UE).

Referring to FIG. 4, a V2X system 400 (for example, including vehicle tovehicle (V2V) communications) is illustrated with two vehicles 402, 404.The first transmission mode allows for direct communication betweendifferent participants in a given geographic location. As illustrated, avehicle can have a wireless communication link 406 with an individual(V2P) (for example, via a UE) through a PC5 interface. Communicationsbetween the vehicles 402 and 404 may also occur through a PC5 interface408. In a like manner, communication may occur from a vehicle 402 toother highway components (for example, highway component 410), such as atraffic signal or sign (V2I) through a PC5 interface 412. With respectto each communication link illustrated in FIG. 4, two-way communicationmay take place between elements, therefore each element may be atransmitter and a receiver of information. The V2X system 400 may be aself-managed system implemented without assistance from a networkentity. A self-managed system may enable improved spectral efficiency,reduced cost, and increased reliability as network service interruptionsdo not occur during handover operations for moving vehicles. The V2Xsystem may be configured to operate in a licensed or unlicensedspectrum, thus any vehicle with an equipped system may access a commonfrequency and share information. Such harmonized/common spectrumoperations allow for safe and reliable operation.

FIG. 5 shows a V2X system 500 for communication between a vehicle 552and a vehicle 554 through a network entity 556. These networkcommunications may occur through discrete nodes, such as a BS (e.g., theBS 110 a), that sends and receives information to and from (for example,relays information between) vehicles 552, 554. The networkcommunications through vehicle to network (V2N) links 558 and 510 may beused, for example, for long range communications between vehicles, suchas for communicating the presence of a car accident a distance aheadalong a road or highway. Other types of communications may be sent bythe node to vehicles, such as traffic flow conditions, road hazardwarnings, environmental/weather reports, and service stationavailability, among other examples. Such data can be obtained fromcloud-based sharing services.

Roadside units (RSUs) may be utilized. An RSU may be used for V2Icommunications. In some examples, an RSU may act as a forwarding node toextend coverage for a UE. In some examples, an RSU may be co-locatedwith a BS or may be standalone. RSUs can have different classifications.For example, RSUs can be classified into UE-type RSUs and MicroNodeB-type RSUs. Micro NB-type RSUs have similar functionality as theMacro eNB/gNB. The Micro NB-type RSUs can utilize the Uu interface.UE-type RSUs can be used for meeting tight quality-of-service (QoS)requirements by minimizing collisions and improving reliability. UE-typeRSUs may use centralized resource allocation mechanisms to allow forefficient resource utilization. Critical information (e.g., such astraffic conditions, weather conditions, congestion statistics, sensordata, etc.) can be broadcast to UEs in the coverage area. Relays canre-broadcasts critical information received from some UEs. UE-type RSUsmay be a reliable synchronization source.

As mentioned above, aspects of the present disclosure relate totechniques for mapping two-stage sidelink control information (SCI) withmulti-layer sidelink data channel.

In certain systems, such as NR systems (e.g., Release 16 NR), atwo-stage SCI is transmitted between user equipment (UEs) in sidelinkcommunications. The two-stage SCI may include a first stage (referred toas SCI-1) and a second stage (referred to as SCI-2).

The SCI-1 may include information regarding resource availability, suchas resource reservation and resource allocation information, andinformation for decoding the SCI-2. The SCI-2 may include at leastinformation for decoding data and information for determining theintended recipient of the transmission.

FIG. 6 is a diagram illustrating example sidelink data channel,demodulation reference signal (DMRS) for the data channel, and two-stageSCI transmission in a slot 600, in accordance with certain aspects ofthe present disclosure. In some example, the SCI-1 is transmitted overthe physical sidelink control channel (PSCCH), as shown in FIG. 6. Insome examples, the SCI-2 may be transmitted over a second PSCCH, asshown in FIG. 6. In some examples, the SCI-2 may be transmitted (e.g.,piggybacked) on the PSSCH (not shown).

According to certain aspects, the DMRS for the sidelink data channel(e.g., the PSSCH) is used to demodulate the SCI-2. For example, thePSSCH DMRS can be used to perform channel estimation for the SCI-2.

In some examples, the PSCCH may use 1 layer; however, the PSSCH can bemore than 1 layer. Thus, the data sidelink channel may use multiplelayers and the SCI-2 may be transmitted using only a single port of themulti-layer PSSCH. When the SCI-2 is sent with multi-layer PSSCH, theremay be a power imbalance.

Accordingly, techniques and apparatus are desirable for mapping thesecond stage of the two-part SCI (e.g., the SCI-2) with a multiple-layersidelink data channel, for example, even when the second stage of thetwo-part SCI and the data sidelink channel use different numbers oflayers.

Example Mapping Two-Stage Sidelink Control with Multi-Layer SidelinkData Channel

As discussed above (e.g., with respect to FIG. 6), sidelink data channeldemodulation reference signals (DMRS) can be used for channel estimationfor a two-stage sidelink control. For example, the second stage (SCI-2)of the two-stage sidelink control information can be demodulated basedon channel estimation using the physical sidelink shared channel (PSSCH)DMRS.

In some systems, a transmitting device, such as a sidelink userequipment (UE), generates bits (e.g., a sequence of information bits)for the SCI-2. The UE may then encode the bits (e.g., using polar code).The encoded bits are then rate-matched. After the rate-matching, thecoded bits may be scrambled and modulated to produce the modulationsymbols. The modulation symbols are then mapped to layers and thenmapped to antenna ports. Precoding may be applied.

According to certain aspects, the UE rate-matches the SCI-2 as if itwere a single layer, even though the PSSCH can be multiple layers. Insome examples, the rate-matching involves bit selection and bitinterleaving. In some examples, the rate-matching includes determiningthe number of coded modulation symbols to map to an antenna port. In anillustrative example, there may be 10 tones and 2 layers PSSCH. In thiscase, for rate-matching as 2 layers, the UE may assume 20 codedmodulation symbols. According to aspects herein, however, the UE mayrate-match the SCI-2 as a single layer. Thus, in the illustrativeexample, the UE may assume 10 code modulation symbols (e.g., the numberof modulation symbols is assumed during the encoding). The rate-matchedSCI-2 is then mapped to an antenna port.

According to certain aspects, when the PSSCH is more than one layer, theother layers of the SCI-2 are repetitions of the SCI-2 on a first layer.The SCI-2 duplicate layers are then mapped to the antenna ports. In someexamples, precoder cycling may be applied. For example, differentprecoders may be used on different precoding resource block groups(PRGs). In some examples, the precoder cycling may be cyclic delaydiversity (CDD) precoder cycling, where different precoders are appliedon different tones.

The sequence of precoders and the precoder resource bundle size (e.g.,the PRGs) may be known to both the transmitter and the receiver devices.For example, the sequence of precoders and/or precoder resource bundlesize may be defined in a wireless specification, preconfigured (e.g., apreloaded configuration), configured (e.g., via a radio resource control(RRC) parameter), or indicated in the SCI-1 (e.g., via an index value).

According to certain aspects, when the PSSCH is more than on layer, theUE applies CDD (e.g., mandatory CDD when more than one layer is used forthe SCI-2). Thus, the output on one antenna port is a cyclicallytime-shifted version of the output on the other antenna ports. In someexamples, the CDD may be achieved by precoder cycling on a per-tonebasis. In some examples, the SCI-2 rate-matching is repeated on themultiple layers, and the precoders are selected to apply the CDD to thelayers.

According to certain aspects, the rate-matching as a single layer,duplicating layers, and/or CCD precoding is applied when a condition issatisfied (e.g., based on the UE determining the condition issatisfied). In some example, the condition is when the PSSCH is morethan one layer. In some examples, the condition is when the SCI-2 isfrequency division multiplexed (FDD) with data. In some examples, thecondition is when the SCI-2 is FDMed with the SCI-1. In some examples,the condition is a combination of the above conditions.

According to certain aspects, the receiving device, such as a secondsidelink UE, receives the SCI-2, decodes the SCI-2, and de-rate matchesthe SCI-2. In some cases, the second UE may choose to receive the SCI-2on only one of the antenna ports. For example, based on a capability ofthe second UE.

According to certain aspects, when a second-stage control layer is arepetition of another, the modulation symbols in that layer may bepermuted relative to the other layers. Permuting the modulations symbolsmay advantageously provide frequency diversity for the sidelink controltransmission.

In some examples, the permutation may be a reversal of themodulation-symbol order. For example, the modulation symbols for asecond, repeated, layer may be in reverse order of the modulationsymbols mapped to the first layer.

In some examples, the permutation may be configured, or preconfigured.In some examples, the permutation may be indicated in the first stage ofthe sidelink control (e.g., SCI-1). For example, a set of differentpermutations may be configured, and the indication of the permutationmay be an index value of one of the configured permutations in the set.

In some examples, whether or not to permute the modulation symbols forthe layers may be configured or preconfigured. In some examples, anindication of whether the modulation symbols are permutated may beindicated in the first stage of the sidelink control (e.g., SCI-1). Insome examples, toggling the permuting may allow the UE to reducecomplexity at times and to increase frequency diversity at other times.

According to certain aspects, although the modulation symbols on thedifferent layers may be permuted, the content (e.g., the information andcoded bits) on each layer is the same. In some examples, the samemodulation symbols are used for the different layers.

FIG. 7 is a flow diagram illustrating example operations 700 forwireless communication, in accordance with certain aspects of thepresent disclosure. The operations 700 may be performed, for example, bya sidelink UE (e.g., such as a UE 120 a in the wireless communicationnetwork 100). Operations 700 may be implemented as software componentsthat are executed and run on one or more processors (e.g.,controller/processor 280 of FIG. 2). Further, the transmission andreception of signals by the UE in operations 700 may be enabled, forexample, by one or more antennas (e.g., antennas 252 of FIG. 2). Incertain aspects, the transmission and/or reception of signals by the UEmay be implemented via a bus interface of one or more processors (e.g.,controller/processor 280) obtaining and/or outputting signals.

Operations 700 may begin, at 702, by rate-matching a multiple-layersecond stage of a two-stage SCI transmission as a single layer. In someexamples, the rate-matching includes determining a number of codedmodulation symbols for second stage of the two-stage SCI based on asingle layer.

According to certain aspects, the first UE maps the number of codedmodulation symbols to an antenna port. In some examples, the first UEduplicates (e.g., repeats) the mapping of the number of coded modulationsymbols on the multiple layers. In some examples, the first UE appliesdifferent precoders for different PRGs (e.g., precoder cycling). In someexamples, the precoders and PRGs are specified at the first UE,configured, or indicated. For example, the first UE can indicate theprecoders and PRGs to the second UE in a first stage of the two-stageSCI.

According to certain aspects, optionally at 704, the first UE appliesCDD to the second stage of the two-stage SCI (e.g., mandatory CDD when acondition is met). For example, the first UE can apply precoder cyclingper-tone. In this case, the second stage is transmitted with a cyclictime-shift at the output of the multiple antenna ports.

At 706, the first UE transmits the multiple-layer second stage of thetwo-stage SCI, to a second UE, using multiple antenna ports.

According to certain aspects, the first UE determines whether acondition is satisfied and performs the SCI-2 rate-matching as a singlelayer based on the determination. In some examples, the first UEdetermines a PSSCH has more than one layer. In some examples, the firstUE determines the second stage of the two-stage SCI is FDMed with data.In some examples, the first UE determines the second stage of thetwo-stage SCI is FDMed with a first stage of the two-stage SCI. In someexamples, the first UE determines a combination of the conditions aremet. The first UE rate-matches the multiple-layer second stage of thetwo-stage SCI transmission as a single layer based on the determination.In some examples, the first UE duplicates the rate-matched SCI-1 on themultiple layers and/or applies CDD precoding to the layers when one ormore of the conditions are met.

According to certain aspects, the two-stage SCI is transmitted with aPSSCH transmission. A first stage of the two-stage SCI may betransmitted on a first PSCCH and may carry resource availabilityinformation. The second stage of the two-stage SCI may be transmitted ona second PSCCH or on the PSSCH and may carry information to decode adata transmission.

FIG. 8 illustrates a communications device 800 that may include variouscomponents (e.g., corresponding to means-plus-function components)configured to perform operations for the techniques disclosed herein,such as the operations illustrated in FIG. 7. The communications device800 includes a processing system 802 coupled to a transceiver 808 (e.g.,a transmitter and/or a receiver). The transceiver 808 is configured totransmit and receive signals for the communications device 800 via anantenna 810, such as the various signals as described herein. Theprocessing system 802 may be configured to perform processing functionsfor the communications device 800, including processing signals receivedand/or to be transmitted by the communications device 800.

The processing system 802 includes a processor 804 coupled to acomputer-readable medium/memory 812 via a bus 806. In certain aspects,the computer-readable medium/memory 812 is configured to storeinstructions (e.g., computer-executable code) that when executed by theprocessor 804, cause the processor 804 to perform the operationsillustrated in FIG. 7, or other operations for performing the varioustechniques discussed herein for mapping two-stage sidelink control withmulti-layer sidelink data channel. In certain aspects, computer-readablemedium/memory 812 stores code 814 for rate-matching a multiple-layersecond stage of a two-stage SCI transmission as a single layer; code 816for applying CDD to the second stage of the two-stage SCI; and/or code818 for transmitting the multiple-layer second stage of the two-stageSCI, to a second UE, using multiple antenna ports, in accordance withaspects of the present disclosure. In certain aspects, the processor 804has circuitry configured to implement the code stored in thecomputer-readable medium/memory 812. The processor 804 includescircuitry 820 for rate-matching a multiple-layer second stage of atwo-stage SCI transmission as a single layer; circuitry 822 for applyingcyclic delay diversity (CDD) to the second stage of the two-stage SCI;and/or circuitry 824 for transmitting the multiple-layer second stage ofthe two-stage SCI, to a second UE, using multiple antenna ports, inaccordance with aspects of the present disclosure.

The techniques described herein may be used for various wirelesscommunication technologies, such as NR (e.g., 5G NR), 3GPP Long TermEvolution (LTE), LTE-Advanced (LTE-A), code division multiple access(CDMA), time division multiple access (TDMA), frequency divisionmultiple access (FDMA), orthogonal frequency division multiple access(OFDMA), single-carrier frequency division multiple access (SC-FDMA),time division synchronous code division multiple access (TD-SCDMA), andother networks. The terms “network” and “system” are often usedinterchangeably. A CDMA network may implement a radio technology such asUniversal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. cdma2000 coversIS-2000, IS-95 and IS-856 standards. A TDMA network may implement aradio technology such as Global System for Mobile Communications (GSM).An OFDMA network may implement a radio technology such as NR (e.g. 5GRA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11(Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, etc. UTRA andE-UTRA are part of Universal Mobile Telecommunication System (UMTS). LTEand LTE-A are releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE,LTE-A and GSM are described in documents from an organization named “3rdGeneration Partnership Project” (3GPP). cdma2000 and UMB are describedin documents from an organization named “3rd Generation PartnershipProject 2” (3GPP2). NR is an emerging wireless communications technologyunder development.

In 3GPP, the term “cell” can refer to a coverage area of a Node B (NB)and/or a NB subsystem serving this coverage area, depending on thecontext in which the term is used. In NR systems, the term “cell” andBS, next generation NodeB (gNB or gNodeB), access point (AP),distributed unit (DU), carrier, or transmission reception point (TRP)may be used interchangeably. A BS may provide communication coverage fora macro cell, a pico cell, a femto cell, and/or other types of cells. Amacro cell may cover a relatively large geographic area (e.g., severalkilometers in radius) and may allow unrestricted access by UEs withservice subscription. A pico cell may cover a relatively smallgeographic area and may allow unrestricted access by UEs with servicesubscription. A femto cell may cover a relatively small geographic area(e.g., a home) and may allow restricted access by UEs having anassociation with the femto cell (e.g., UEs in a Closed Subscriber Group(CSG), UEs for users in the home, etc.). A BS for a macro cell may bereferred to as a macro BS. A BS for a pico cell may be referred to as apico BS. A BS for a femto cell may be referred to as a femto BS or ahome BS.

A UE may also be referred to as a mobile station, a terminal, an accessterminal, a subscriber unit, a station, a Customer Premises Equipment(CPE), a cellular phone, a smart phone, a personal digital assistant(PDA), a wireless modem, a wireless communication device, a handhelddevice, a laptop computer, a cordless phone, a wireless local loop (WLL)station, a tablet computer, a camera, a gaming device, a netbook, asmartbook, an ultrabook, an appliance, a medical device or medicalequipment, a biometric sensor/device, a wearable device such as a smartwatch, smart clothing, smart glasses, a smart wrist band, smart jewelry(e.g., a smart ring, a smart bracelet, etc.), an entertainment device(e.g., a music device, a video device, a satellite radio, etc.), avehicular component or sensor, a smart meter/sensor, industrialmanufacturing equipment, a global positioning system device, or anyother suitable device that is configured to communicate via a wirelessor wired medium. Some UEs may be considered machine-type communication(MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include,for example, robots, drones, remote devices, sensors, meters, monitors,location tags, etc., that may communicate with a BS, another device(e.g., remote device), or some other entity. A wireless node mayprovide, for example, connectivity for or to a network (e.g., a widearea network such as Internet or a cellular network) via a wired orwireless communication link. Some UEs may be consideredInternet-of-Things (IoT) devices, which may be narrowband IoT (NB-IoT)devices.

The methods disclosed herein comprise one or more steps or actions forachieving the methods. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover a, b, c,a-b, a-c, b-c, and a-b-c, as well as any combination with multiples ofthe same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b,b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c).

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “determining” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” may include resolving, selecting, choosing, establishingand the like.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language of the claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. All structural andfunctional equivalents to the elements of the various aspects describedthroughout this disclosure that are known or later come to be known tothose of ordinary skill in the art are expressly incorporated herein byreference and are intended to be encompassed by the claims. Moreover,nothing disclosed herein is intended to be dedicated to the publicregardless of whether such disclosure is explicitly recited in theclaims. No claim element is to be construed under the provisions of 35U.S.C. § 112(f) unless the element is expressly recited using the phrase“means for” or, in the case of a method claim, the element is recitedusing the phrase “step for.”

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software component(s)and/or module(s), including, but not limited to a circuit, anapplication specific integrated circuit (ASIC), or processor. Generally,where there are operations illustrated in figures, those operations mayhave corresponding counterpart means-plus-function components withsimilar numbering.

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device (PLD),discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

If implemented in hardware, an example hardware configuration maycomprise a processing system in a wireless node. The processing systemmay be implemented with a bus architecture. The bus may include anynumber of interconnecting buses and bridges depending on the specificapplication of the processing system and the overall design constraints.The bus may link together various circuits including a processor,machine-readable media, and a bus interface. The bus interface may beused to connect a network adapter, among other things, to the processingsystem via the bus. The network adapter may be used to implement thesignal processing functions of the PHY layer. In the case of a userterminal 120 (see FIG. 1), a user interface (e.g., keypad, display,mouse, joystick, etc.) may also be connected to the bus. The bus mayalso link various other circuits such as timing sources, peripherals,voltage regulators, power management circuits, and the like, which arewell known in the art, and therefore, will not be described any further.The processor may be implemented with one or more general-purpose and/orspecial-purpose processors. Examples include microprocessors,microcontrollers, DSP processors, and other circuitry that can executesoftware. Those skilled in the art will recognize how best to implementthe described functionality for the processing system depending on theparticular application and the overall design constraints imposed on theoverall system.

If implemented in software, the functions may be stored or transmittedover as one or more instructions or code on a computer readable medium.Software shall be construed broadly to mean instructions, data, or anycombination thereof, whether referred to as software, firmware,middleware, microcode, hardware description language, or otherwise.Computer-readable media include both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. The processor may beresponsible for managing the bus and general processing, including theexecution of software modules stored on the machine-readable storagemedia. A computer-readable storage medium may be coupled to a processorsuch that the processor can read information from, and write informationto, the storage medium. In the alternative, the storage medium may beintegral to the processor. By way of example, the machine-readable mediamay include a transmission line, a carrier wave modulated by data,and/or a computer readable storage medium with instructions storedthereon separate from the wireless node, all of which may be accessed bythe processor through the bus interface. Alternatively, or in addition,the machine-readable media, or any portion thereof, may be integratedinto the processor, such as the case may be with cache and/or generalregister files. Examples of machine-readable storage media may include,by way of example, RAM (Random Access Memory), flash memory, ROM (ReadOnly Memory), PROM (Programmable Read-Only Memory), EPROM (ErasableProgrammable Read-Only Memory), EEPROM (Electrically ErasableProgrammable Read-Only Memory), registers, magnetic disks, opticaldisks, hard drives, or any other suitable storage medium, or anycombination thereof. The machine-readable media may be embodied in acomputer-program product.

A software module may comprise a single instruction, or manyinstructions, and may be distributed over several different codesegments, among different programs, and across multiple storage media.The computer-readable media may comprise a number of software modules.The software modules include instructions that, when executed by anapparatus such as a processor, cause the processing system to performvarious functions. The software modules may include a transmissionmodule and a receiving module. Each software module may reside in asingle storage device or be distributed across multiple storage devices.By way of example, a software module may be loaded into RAM from a harddrive when a triggering event occurs. During execution of the softwaremodule, the processor may load some of the instructions into cache toincrease access speed. One or more cache lines may then be loaded into ageneral register file for execution by the processor. When referring tothe functionality of a software module below, it will be understood thatsuch functionality is implemented by the processor when executinginstructions from that software module.

Also, any connection is properly termed a computer-readable medium. Forexample, if the software is transmitted from a website, server, or otherremote source using a coaxial cable, fiber optic cable, twisted pair,digital subscriber line (DSL), or wireless technologies such as infrared(IR), radio, and microwave, then the coaxial cable, fiber optic cable,twisted pair, DSL, or wireless technologies such as infrared, radio, andmicrowave are included in the definition of medium. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Thus, in some aspects computer-readable media maycomprise non-transitory computer-readable media (e.g., tangible media).In addition, for other aspects computer-readable media may comprisetransitory computer-readable media (e.g., a signal). Combinations of theabove should also be included within the scope of computer-readablemedia.

Thus, certain aspects may comprise a computer program product forperforming the operations presented herein. For example, such a computerprogram product may comprise a computer-readable medium havinginstructions stored (and/or encoded) thereon, the instructions beingexecutable by one or more processors to perform the operations describedherein, for example, instructions for performing the operationsdescribed herein and illustrated in FIG. 7.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a user terminal and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a userterminal and/or base station can obtain the various methods uponcoupling or providing the storage means to the device. Moreover, anyother suitable technique for providing the methods and techniquesdescribed herein to a device can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

1. A method for wireless communications by a first user equipment (UE),comprising: rate-matching a multiple-layer second stage of a two-stagesidelink control information (SCI) transmission as a single layer; andtransmitting the multiple-layer second stage of the two-stage SCI, to asecond UE, using multiple antenna ports.
 2. The method of claim 1,wherein the rate-matching comprises: determining a number of codedmodulation symbols for the second stage of the two-stage SCI based on asingle layer.
 3. The method of claim 2, further comprising: mapping thenumber of coded modulation symbols to an antenna port.
 4. The method ofclaim 3, further comprising mapping the coded modulation symbols to eachof the multiple antenna ports.
 5. The method of claim 1, whereintransmitting the multiple-layer second stage of the two-stage SCI, tothe second UE, using the multiple antenna ports comprises: repeating afirst layer of the multiple-layer second stage of the two-stage SCI oneach of the multiple layers.
 6. The method of claim 5, furthercomprising permuting modulation symbols for the first layer and themultiple layers.
 7. The method of claim 6, wherein permuting themodulation symbols comprises ordering the modulation symbols for asecond layer in reverse order of the modulation symbols for the firstlayer.
 8. The method of claim 6, wherein the permuting is configured orpreconfigured.
 9. The method of claim 6, wherein a first stage of thetwo-stage SCI indicates the permutating.
 10. The method of claim 9,wherein a plurality of permutation patterns are configured, and whereinthe first stage of the two-stage SCI includes an index of one of theplurality of configured permutation patterns.
 11. The method of claim 5,wherein the same information and coded bits are transmitted on each ofthe layers.
 12. The method of claim 1, further comprising applying adifferent precoder for each precoder resource block group (PRG).
 13. Themethod of claim 12, wherein the precoders and PRGs are specified at thefirst UE, configured, or indicated.
 14. The method of claim 13, furthercomprising indicating the precoders and PRGs to the second UE in a firststage of the two-stage SCI.
 15. The method of claim 1, furthercomprising applying cyclic delay diversity (CDD) to the second stage ofthe two-stage SCI.
 16. The method of claim 15, wherein applying the CDDcomprises applying precoder cycling per-tone.
 17. The method of claim15, wherein transmitting the second stage of the two-stage SCI comprisestransmitting the second stage with a cyclic time-shift at the output ofan antenna port.
 18. The method of claim 1, further comprising:determining a physical sidelink shared channel (PSSCH) has more than onelayer, wherein the rate-matching the multiple-layer second stage of thetwo-stage SCI transmission as a single layer is based on thedetermination.
 19. The method of claim 1, further comprising:determining the second stage of the two-stage SCI is frequency divisionmultiplexed (FDM) with data, wherein the rate-matching themultiple-layer second stage of the two-stage SCI transmission as asingle layer is based on the determination.
 20. The method of claim 1,further comprising: determining the second stage of the two-stage SCI isfrequency division multiplexed (FDM) with a first stage of the two-stageSCI, wherein the rate-matching the multiple-layer second stage of thetwo-stage SCI transmission as a single layer is based on thedetermination.
 21. The method of claim 1, wherein: the two-stage SCI istransmitted with a physical sidelink shared channel (PSSCH)transmission; a first stage of the two-stage SCI is transmitted on afirst physical sidelink control channel (PSCCH) and carries resourceavailability information; and the second stage of the two-stage SCI istransmitted on a second PSCCH or on the PSSCH and carries information todecode a data transmission.
 22. An apparatus for wirelesscommunications, comprising: at least one processor; and a memory coupledto the at least one processor, the memory comprising code executable bythe at least one processor to cause the apparatus to: rate-match amultiple-layer second stage of a two-stage sidelink control information(SCI) transmission as a single layer; and transmit the multiple-layersecond stage of the two-stage SCI, to another apparatus, using multipleantenna ports.
 23. The apparatus of claim 22, wherein the memorycomprising code executable by the at least one processor to cause theapparatus to rate-matching comprises: code executable by the at leastone processor to cause the apparatus to determine a number of codedmodulation symbols for the second stage of the two-stage SCI based on asingle layer.
 24. The apparatus of claim 23, wherein the memory furthercomprises code executable by the at least one processor to cause theapparatus to: map the number of coded modulation symbols to an antennaport.
 25. The apparatus of claim 24, wherein the memory furthercomprises code executable by the at least one processor to cause theapparatus to map the coded modulation symbols to each of the multipleantenna ports.
 26. The apparatus of claim 22, wherein the memorycomprising code executable by the at least one processor to cause theapparatus to transmit the multiple-layer second stage of the two-stageSCI, to the other apparatus, using the multiple antenna ports comprises:code executable by the at least one processor to cause the apparatus torepeat a first layer of the multiple-layer second stage of the two-stageSCI on each of the multiple layers.
 27. The apparatus of claim 26,wherein the memory further comprises code executable by the at least oneprocessor to cause the apparatus to permute modulation symbols for thefirst layer and the multiple layers.
 28. The apparatus of claim 27,wherein the memory comprising code executable by the at least oneprocessor to cause the apparatus to permute the modulation symbolscomprises code executable by the at least one processor to cause theapparatus to order the modulation symbols for a second layer in reverseorder of the modulation symbols for the first layer.
 29. An apparatusfor wireless communications, comprising: means for rate-matching amultiple-layer second stage of a two-stage sidelink control information(SCI) transmission as a single layer; and means for transmitting themultiple-layer second stage of the two-stage SCI, to another apparatus,using multiple antenna ports.
 30. A computer readable medium storingcomputer executable code thereon for wireless communications by a firstuser equipment (UE), comprising: code for rate-matching a multiple-layersecond stage of a two-stage sidelink control information (SCI)transmission as a single layer; and code for transmitting themultiple-layer second stage of the two-stage SCI, to a second UE, usingmultiple antenna ports.